It is known for vehicles, such as automobiles and aircraft, to include an electronic display providing an image of, for example, an instrument cluster for replacing discrete mechanical or electrical dials. However, such displays are generally aesthetically limited because of their inability to produce images that differ from the standard two dimensional (2D) images displayed in the plane of the display. In addition to reducing the aesthetics of such displays, the inability to produce images that do not appear flat may provide limited realism of such displays. Although stereoscopic and autostereoscopic displays are known and can produce an impression of a three-dimensional image, such displays may produce eye strain and headache problems because of a potential limited freedom of viewing position and focussing issues.
It is also known for advertising displays, such as for example large-area public displays in shopping centres and digital signage displays on motorways, to aim for catching maximum attention from people. Although such displays become more and more common, they generally do not feature any aesthetically appealing features, aside from their large size, that would make them stand out of the ordinary and facilitate their acceptance. Overcoming the inability of such displays to produce images different from standard flat 2D images displayed in the plane of the display may therefore contribute to favour their widespread acceptance.
A first general class of prior art teaches how to make stereoscopic and auto-stereoscopic displays from a single panel. For example, FIG. 1 of the accompanying drawings illustrates a switchable 2D/3D (two dimensional/three dimensional) display based on the use of a parallax barrier, as disclosed in EP0829744. The parallax barrier comprises a polarisation-modifying layer 50, with alternating aperture regions 51 and barrier regions 52, and a polariser in the form of a polarisation sheet 53 which may be disabled. The parallax element provides the possibility of operating the display in a wide view full resolution 2D mode or in a directional 3D autostereoscopic mode. However, this device produces a stereo image pair to generate 3D images rather than images with curved-appearance. Drawbacks of auto-stereoscopic displays include limited head freedom and inconsistency between 3D perception from stereo and from other cues (head motion, focus), leading to user confusion and sometimes eye strain and headaches.
A second general class of prior art is related to curved or conformal displays. For example, FIG. 2 of the accompanying drawings shows a display of the type disclosed in WO94/11779. A curved liquid crystal display is manufactured by sandwiching a liquid crystal layer 54 between two curved pre-shaped transparent plastic substrates 55 or between two flexible substrates.
As illustrated in FIG. 3 of the accompanying drawings, US2006/0098153A1 discloses a display device of the same type but where a curved display is formed by manufacturing a flat panel display layer 56 and thereafter curving the display layer itself by adhering an additional film 57 to it. The additional film may for example have been pre-stretched and the contraction force it releases after adhesion to the display results in the bending of the display.
Although these curved display devices are able to generate curved images, they both rely on displays which have been physically bent in order to produce the desired curvature. Such curved displays have many disadvantages, such as very high cost, limitations in material efficiency and material diversity, and strong difficulty in manufacturing. Further, displays of this type are very limited in their design as the variety of feasible curved-shapes is limited and, once a display has been manufactured with a specific curvature, this cannot be changed. Also, curved displays are not ready for mass-production yet as each production line would need to adapt to a particular curved design.
A final class of prior art concerns displays using projection onto curved surfaces. For example, U.S. Pat. No. 6,727,971 and U.S. Pat. No. 6,906,860 disclose a display of the type illustrated in FIGS. 4a and 4b, respectively, of the accompanying drawings. In both cases, the display comprises at least one projector 58 and a curved screen 59, onto which is projected an image.
Such displays are well-known from the public area and are used for many applications such as the reconfigurable display from Digital Dash or immersive displays. However, they have the disadvantage of requiring a large space and being limited to projection technology only. Also, they are generally defined as constituting a display when considering together the projection system associated with the curved screen and not the projection system by itself.
GB2437553 discloses a family of dual- and multiple-depth displays where a multiple-depth image is generated from a single display panel. Optical elements are placed a short distance in front of a display panel to produce differing depth effects from different optical paths. By use of polarisation effects and partial reflections, different images are associated with light paths of different lengths and appear to originate from different planes. By displaying these images time-sequentially or spatially-interlaced, a multiple-depth effect is achieved.
An embodiment from GB2437553 is shown in FIGS. 5a and 5b of the accompanying drawings. First and second partial reflectors 61 and 62 are placed in front of a liquid crystal display (LCD) panel 60 with polarisation-modifying optics 63 disposed between the first and second reflectors 61 and 62. The first and second reflectors 61 and 62 are separated from each other by an appropriate spacing for producing a depth-shifted image. Light from two different images displayed by the LCD panel 60 travels along different light paths towards the viewer. Light encoding the first image passes directly by transmission through the optical system to the viewing region as shown in FIG. 5b, whereas light encoding the second image follows a “zig-zag” path 64 before reaching the viewer as shown in FIG. 5a. As a result of the different lengths of the different paths 64 and 65, the first image appears at the location of the LCD 60, whereas the second image 66 of the LCD is shifted in depth so as to appear below the LCD. The viewer thus observes images in different depth planes.
Displays of this type have clear advantages over multiple-depth displays using multiple display panels, for example in terms of cost, brightness and volume. However, the main purpose of these displays is to create two images, or more, separated in depth. In addition, the partial reflectors in the optical system of such displays are parallel to each other and to an image surface of the display.
When two images must be presented independently to a viewer from the same underlying display device, there is some leakage or crosstalk between the views and this may be corrected by modifying the image data sent to the display. Crosstalk is effectively removed, but there is also a loss of contrast.
EP0953962 discloses crosstalk correction in 3D and dual-view displays. For these two types of display, crosstalk tends to be symmetric and colour-independent. In other words, the leakage from image 1 to image 2 is the same as the leakage from image 2 to image 1, and also the same for red, green and blue components of the image.
GB2437553 discloses the same basic principle of crosstalk correction but applied to dual-depth displays. For this type of display, crosstalk tends to depend upon the direction of leakage as well as on colour.